Isomerism Flashcards
Another word forEZ isomerism
And what is needed for it to occur?
Geometric isomerism
A carbon - carbon double bond to prevent rotation, and 2 different groups attached to the carbon atom
What is optical isomerism
When isomers have the same molecular and structural formula, but have a different affect in the plane of polarised light
What are enantiomers
Non super impossible mirror images
Why can’t a carbon atom that’s part of a double bond or a carbonyl (C=O) atom not be chiral?
Due to the mirror image relationship and the fact isomers can’t be superimposed on eachother, it can’t be chiral as the carbons only have 3 Different atoms or groups attached
How does optical isomerism arise?
It arises from molecules which have 4 different atoms or groups of atoms attached to the tetrahedral carbon (chiral)
Describe an optically active compound (enantiomer)
It has the ability to rotate the plane of polarised light left or right, amount of rotation is measured by a polarimeter
What is an equivocal mixture of 2 different enantiomers called?
Race mate
Why is a race mate (equinmolar mixture of 2 enantiomers) optically INACTIVE?
Because the rotating effect of one enantiomer cancels out the effect of another
What is the separation of a race mate into component enantiomers called?
Resolution
What is a stereoisomer?
Have same molecular and structural formula but atoms arranged differently in space
How can you distinguish between enantiomers?
Rotate the plane of polarised light in opposite directions
What is the amount of rotation measured using?
A polarimeter
Ratio of an equinmolar mixture of 2 enantiomers (racemate)
1:1
An equinmolar mixture of 2 enantiomers is optically inactive- why?
The rotating effect of one enantiomer cancels out the effect of another
Define an enantiomer and its ability
Non superimposable mirror images
Has the ability to rotate the plane of polarised light left or right
Is an enantiomer optically active or inactive?why?
Active !
Because it has the ability to rotate the plane of polarised light left or right
Give some examples of Carbons / compounds that aren’t Chiral
Why?
C=O
C=C
Benzene
Due to the mirror image relationship and the fact isomers cannot be superimposed on eachother - must have 4 different atoms attached to the tetrahdral (chiral) Carbon!
What is meant by a compound that shows optical activity
Has ability to rotate the plane of polarised light in opposite directions
Why is something optically inactive
Rousting effect of one enantiomer cancels out affect of another
What is meant by the term enantiomer
An optically active isomer that had the ability to rotate the plane of polarised light in opposite directions
